Rob Schneider on P. Seligman (1942- ) Character Strengths and Virtues: A Handbook and Classification (2004); he was a pioneer in documenting empirical evidence of the link between optimism, physical health, and longevity. Piaget, Jean (1896-1980) Swiss child psychologist and epistemologist: his theoretical and research work on the stages of cognitive development in children was enormously influential (see PIAGETIAN THEORY); he also proposed a stage theory of moral development (see, e.g., AuTONOMOus stage) and was a central proponent of the theoretical perspective known as constructivism. Pick, Herbert L., Jr. Rob Schneider 2016.